Thread: help needed 8' x4' cnc

Hi Guys
Back from Adelaide
First off

Huge thank you to Chris.. Plenty of information and it was great to see the CNC in action and from all the angles!!!! Thanks again!!!
Now been to the steel guys
and took some photos
Attachment 235306Attachment 235308Attachment 235309Attachment 235307
The table in photos is actually two I beams (approx 70mm width x 120mm height ) sitting on two sets of legs (which are bolted)
Now the sizes..
The I beam lenghth is about 3.5 metres.. One of the I beams has some plates welded on at the end (see photo one) which can be removed or I beams cut which will still give me more than 3 metres length
I beam are joined with adjustable bar allowing table to stretch / shrink as required (see photo two and three) giving max width of approx 1400mm internal
Legs are on adjustable feet.. (nice touch)
Now although covered in rust.. the top was machined and looks pretty much flat..
I think this could actually work as an CNC table.. (thinking of adding additional pair of legs in the middle to prevent any flexing and extra bars joining two sides...
He's asking for $200 which is a bargain (special friends rate..
estimated steel cost would be about $500 hence that's why he has bought it to start with...
Best part is that legs and beams can be taken apart allowing for transport..
So guys what do you think?? worth getting it???
I guess with extra bars and legs it would cost me approx $300.. so any suggestions??
Sorry couldn't get better photos as table was completery covered with various bits and pieces
EDIT : actually displaying pictures rather than links..

Also take into account the I beam machining cost, it wouldn't be cheap.

I reckon its a good starting base, looks heavy

Seems like it could work no worries but personally i would be looking at building from scratch. There are still lots of bits and pieces to be added to the frame anyway. Your consideration was for the table to be moveable, and by extending the table length well beyond the size you need just adds alot of extra costs for rails, rack, cables and so on because of the extended sizes, transport etc.

Also note, that the inside width you mention is 1400mm... you would need to make sure that the z axis you design/buy will be less than 155mm wide (Eq. 1400mm - 1220mm - ~25mm = ~155mm wide MAX). The ~25mm, or 12.5mm both sides, should be substitued for the largest profiling bit you think you will use and also to act as an overshoot to make sure you can cut the entire sheet. I allowed 50mm on my machine for a large ogee bit which was to be used for a small project. This was great but i ended up being very tight to a full sheet due to the length of my rails (Got a good deal on a set of rails that someone had cut without thinking of the above so designed machine around them) and my z axis was wider than first thought, so its cramped the cutting size and although i have not often cut the full width of a sheet(sometimes requires size adjustment to shy of a full sheet), it does still bug me sometimes. Just food for thought.

Daniel

Well I was thinking...
Use I beams and cut them to 3000mm lengths (keep ofcutts and use them as anvil... )
I wasn't really happy with the 1400mm depth either.. but it was a good starting poing...

Now the current idea is...
Use the table as is... .. get the steel guy to cut it at 3000mm lenght (or a bit longer.. ) gotta check the capacity of our van.. see if I can fit 3100 lengths ... (I guess the longer the better)
Get him to make me maybe 1500mm long spreaders for width which will be bolted on (somehow) and put about 4 - 5 of them
Legs can stay but thinking of putting one extra set through middle

Being an I beam I can use underside and mount rack onto it (as seen on Chris's CNC .. thanks again Chris!!! )
Would need to pick your brain where did you get that nice double sided tape... hehe

[QUOTE=Prle77;1553400]Hi guys
I'm thinking of building an CNC which would be able to work on full plywood sheet size... 1200x2400




I have attached photo's of a CNC router that I comissioned to be built for me 10 years ago....It was built to be able to machine 2700 x 1200 panels.

The table size is 3100 x 1500.

The top frame is out of 150 x 75 channel fully welded.
Legs are 100 x 100 RHS...base is bolted to the top frame.

25mm round linear rails supported

X & Y Rack and pinion drive...Z ballscrew

Gantry 200 X 100 RHS...12mm steel ends

Vacuum hold down is a must for panel work.

Hope this gives you some further info.

Cheers,
Kym

Nice looking machine Kym. What DOC do you get with a 1/4in router bit and 1/2 router bit? Do you get much jitter during heavy cuts as those gantry sides look a little thin?

Good example of what can be built.

Daniel

EDIT: this updated forum really hates IE... had to retype post...

[QUOTE=Kym A;1559992
Vacuum hold down is a must for panel work.

Hope this gives you some further info.

Cheers,
Kym[/QUOTE]
Hi Kym
Looks great!!!
lots of ideas and even more questions
What do you use for vacuum ?? Dust collector?? I've got small 1.5HP which i don't think it will be sufficient .. but happy to upgrade... hehe

Any chance you can put some photos from underneath to see how its all connected?? Thanks
Alen

Large CNCd.JPGLarge CNCa.JPGLarge CNCb.JPGLarge CNCc.JPG

Originally Posted by Prle77

EDIT: this updated forum really hates IE... had to retype post...


Hi Kym
Looks great!!!
lots of ideas and even more questions
What do you use for vacuum ?? Dust collector?? I've got small 1.5HP which i don't think it will be sufficient .. but happy to upgrade... hehe

Any chance you can put some photos from underneath to see how its all connected?? Thanks
Alen

Here are some pic's of the vacuum pipe 40mm pvc pipe....the bed is divided into 4 sections that can be on or off suction depending on the size of the panel being machined.
I am using an old old dairy pump for my vacuum.
I have a dust pick up with skirt that I mount under the router when machining panels.

I usually cut out the panels with 2 passes...the 12mm steel gantry ends a quite ridgid.

Cheers,
Kym

Thanks Kym
great photos

considering what you've used for vacuum I seriously doubt my small dust collector will cut it..
Perhaps 3HP one might work.. I'm assuming your base is done as an sandwich.. seeing the top of it where you trenched the squares I would assume each intersection would have a hole??

Originally Posted by Prle77

Thanks Kym
great photos

considering what you've used for vacuum I seriously doubt my small dust collector will cut it..
Perhaps 3HP one might work.. I'm assuming your base is done as an sandwich.. seeing the top of it where you trenched the squares I would assume each intersection would have a hole??

There are 2 suction holes in each pod....the top is 25mm MDF.
I have also sealed it (lacquered) to assist in maximum suction.

Hi guys..
Looking into the electronics part of the 8' x 4' cnc
So I'm asking for suggestions/ comments / info before actually ordering goods
All parts are from homann who was very helpful (thank you)
this is the list I have in mind so please let me know if I this covers everything I need for the CNC

1 x BOB MB-02-V6 Bidirectional Breakout Board 4 x G203V Gecko Vampire stepper drive 1 x PS-10 MeanWell 36Vdc 9.7A Switch Mode Power Supply NES-350-36 (For 387 steppers) 2 x 387 Oz0in NEMA 24 Stepper Motor (Dual Shaft) 24H290-35-4B (Y and Z axis) 2 x PS-01 MeanWell 48VDC 7.3 A Switch Mode Power Supply (for 600 steppers) 2 x 600 Oz-in NEMA34 Stepper 34H280-60-4A (X axis) 20 metres 22 AWG four core shielded stepper motor cable 1 x MACH 3 licence (well lets keep it legit hey???) 4 x omron limit microswitch with roller (2 for X axis stepper alignment, 1 for Y and 1 for Z) 1 x Auxilliary latching emergency stop switch (just in case!!!) Thanks in advance

Did Peter advise you to use the 203Vs for your machine? If he did then take his advice, but otherwise lookat the Gecko 540 drives instead - much cheaper and lots neater.

Think also of the myriad nuts and bolts that you will need, plus the drill and taps they will need as well.
Chain cable carrier.

Also, things such as motor mounts, motor couplings, VFD and spindle, paint even.

Hi Bob
Thanks for reply
trying to split the planing process in stages...
Currently I'm sorting the electronics bare necessities such as what do I need to drive XYZ axis...
Originally I was going for the G540 kit with 3 x 387 steppers.. but after seeing Chris's mechmate figured out that gantry will be quite heavy so decided to go down 600 steppers...
After very informative talk to Peter he advised me to use Vampires because G540 won't be able to drive 600 steppers.. So I have decided to follow his recommendation.. but would like to check with you guys whether I have missed something or whether there's better way???
The above setup is a bit more expensive than the original G540 kit but hey.. rather get it right first time than endlesly purchase parts which won't work (or would uderperform)

Stick with the better drives, G203v if your not right up on your electronics or G201 if you know your stuff(if you want to save a few bucks). Nothing wrong with the G540 but for such a large machine it will be pushed to the limits and allows any upgrades later in stepper size if need be.

Your list is quite well thought out and by the looks has been "adjusted" after some talk with Peter maybe? lol. Only recommendation, if your comfortable with them, is to leave out the limit switches and change to prox switches. Also note you will need a logic supply of 5v. Some take it from the computer PSU but a separate supply from Peter is cheap enough.

Not sure how far your looking atm or how in depth your looking to build the electronics, but there is also quite a bit more in the enclosure i recommend you look at like a mains disconnect switch or contactor setup to switch the power since you will be pulling quite a few amps from the wall socket and youll something rated to do so.

Also buy a good earth wire to ground chassis, enclosure etc.

Keeping legit, you'll also need to start thinking about your software Vcarve, aspire, artcam etc etc etc.